Adhesive hot melt systems may include an applicator for applying a hot melt adhesive onto a substrate. Conventional applicators include a supply block, an adapter and a nozzle secured to the adapter. The nozzle may be formed as a die extruder assembly configured as a contact-type nozzle to directly apply the hot melt adhesive to the substrate. That is, the die extruder assembly does not discharge the hot melt adhesive over a gap onto the substrate. Rather, the substrate is in contact with the hot melt adhesive as the substrate is fed by the die extruder and the adhesive is discharged from the assembly.
In some applications, it is desirable to apply different materials to the substrate. For example, it may be desirable to apply two materials that bond together on the substrate. In a known application, a first material may be a low temperature material that degrades at temperatures over 110 C, while the second material is a material that flows best at a temperature of 150 C.
In current systems, the first and second materials are applied to the substrate by different applicators. Thus, the first material may be applied first and the second material may be applied after the first material. However, in these systems, the first material has a propensity for being wiped off the substrate when the second material is applied by a contact type nozzle or die assembly. To address this, the first material may be applied with a contact die and the second material may be applied with a non-contact spray type nozzle (i.e., the second material is discharged from the nozzle over a gap onto the substrate). However, this necessitates two applicators and complicated handling of the substrate, as two passes are required. Further, additional time is required to make the two passes. Further still, non-contact nozzles require a slower line speed, compared to contact applications, to ensure a suitable application of the material onto the substrate.
In addition, hot melt adhesives have a limited open or bond time, where joining of two materials bonded by the hot melt adhesive can take place. The extra time and space for two applicators is not optimal for this purpose.
Accordingly, it is desirable to provide a single applicator that can apply two separate and overlapping patterns of materials having different temperature parameters in a single pass.